Project 2: Astrocyte-related molecular mechanisms underlying altered neuronal plasticity in Down syndrome The goal of this project is to understand the molecular mechanisms associated with abnormal astrocyte function and their role in altered structural and functional plasticity in the Down's syndrome (DS) brain. Astrocytes are critical regulators of neuronal stem cells (NSCs) proliferation and differentiation as well as dendritic spine development and synaptogenesis. We found metabolic deficits in DS astrocytes directly associated with reduced NSCs viability and aberrant spine formation. To investigate the molecular pathways associated with abnormal astrocyte function and its role in DS altered structural and functional neuroplasticity we propose: 1. To identify the molecular alterations in OS astrocytes responsible for impaired NSCs neurogenesis and spine pathology. We will define the role of intracellular AU and mitochondrial dysfunction in astrocyte secretory deficits, and the role of reduced APPs and thrombospondin 1 (TSP-1) secretion in NSCs and spine pathology. 2. To analyze the effectiveness of mitochondrial cofactors and B-secretase inhibitors to prevent or revert DS astrocyte secretory deficits and concomitant NSCs and spine alterations. 3. A) To study the relation between astrocyte alterations, neurogenesis and spine anomalies in DS brains. We will generate normative data on the association between astrocyte alterations and NSCs and spine deficits in DS individuals. B) To assess the usefulness of TSP-1 levels in CSF and plasma as a biomarker of AD. We propose to perform preliminary studies to evaluate the usefulness of TSP-1 levels in plasma and CSF as a biomarker of AD in sporadic AD and DS+AD patients. We will take advantage of our extensive experience culturing primary human nerve cells derived from fetal brain tissue. NSCs cultures in the form of neurospheres, pure astrocyte cultures, and cocultures of rat hippocampal neurons growing on top of human astrocytes (normal and DS) will be utilized for aims 1 and 2. Aim 3 will utilize post-mortem brain samples and CSF and plasma samples provided by the Neuropathology Core. The Statistical Core will provide feedback in all statistical procedures.